Manifold imaging process employing static charge field application

ABSTRACT

An imaging process wherein a cohesively weak electrically photosensitive imaging layer sandwiched between a donor sheet and a receiver sheet. The sandwich is subjected to an electric field which field is supplied by a static charge in at least one of the donor and receiver sheets. The imaging layer is exposed to imagewise electromagnetic radiation to which it is sensitive and upon separation of the donor and receiver sheet, the imaging layer fractures in imagewise configuration providing a negative image on one of the sheets and a positive image on the other.

finitenl initiates Patet Inventors llvar T. lllirohn;

Geollfrey A. Page; Gedeminas .1. lReinis, s11 of Rochester, NY.

Feb. 28, 1969 Oct. 26, 197 1 Xerox Corporation Rochester, NY.

Continuation-impart 01 application Ser. No. 609,057, Jan. 113, 1967, now abandoned.

Appl. No. Filed Patented Assignee MANHFOLID IMAGING PWJOCESS EMPLOYING STATE! CHARGE WELD AlPlPLllCATlION 20 Claims, 2 Drawing lFigs.

1.1.8. 131 96/l.3, 96/1.4,96/1 R, 204/180, 204/181 llnt. 1 603g 13/22 lFielld 01 Search 96/1, 1.3, 1.4; 204/180, 181

[56] References Cited UNITED STATES PATENTS 2,949,848 8/1960 Mott 101/1283 3,234,019 2/1966 Hall 96/1 3,268,331 8/1966 Harper. 96/1 3,384,566 5/1968 Clark.v 204/181 3,397,086 8/1968 Bartfei 117/218 frimary Examiner-George F. Lesmes Assistant ExaminerJohn C. Cooper 111 Attorneys-James J. Ralabate, Raymond C. Loyer and David C. Petre MANTIFOlLll) TMAGHNG PROCESS EMPLOYIING STATIC CHARGE FIELD AlPlPlLllCA'lllON This application is a continuation-in-part of application ser. No. 609,057 filed Jan. 13, 1967, now abandoned.

BACKGROUND OF THE llNVENTlON The present invention relates in general to imaging and more specifically to an improved process for the formation of images by layer transfer in image configuration.

Although imaging techniques based on layer transfer of a colored material have been known in the past, these techniques have always been clumsy and difficult to operate because they depend upon photochemical reactions and generally involve the use of distinct layer materials for the two functions of imagewise transfer and image coloration. A typical example of the complex structures and sensitive materials employed in prior art techniques is described in U.S. Pat. No. 3,091,529 to Buskes. A more comprehensive discussion of prior art-imaging techniques based on layer transfer may be found in copending application, Ser. No. 45 2,641 filed May 3, 1965 in the U.S. Pat. Office.

There has been discovered a layer transfer imaging process wherein a cohesively weak electrically photosensitive material is sandwiched between two sheets and is fractured in imagewise configuration by the combined effects of electromagnetic radiation and an electric field. There are many means known in the art to provide an electric field, however, the layer transfer imaging process, commonly termed the manifold imaging process, poses unique problems. The manifold imaging process utilizes a manifold sandwich comprising an electrically photosensitive material positioned between a pair of sheets. in this imaging system, an imaging layer is prepared conventionally by coating a layer of photosensitive imaging material onto a substrate. In one form imaging layer comprises a photosensitive material such as metal-free phthalocyanine dispersed in a binder. This coated substrate is called a donor. The other sheet is commonly termed a receiver. An electric field is applied across this manifold sandwich conventionally while it is exposed to a pattern of light and shadow representative of the image to be reproduced. Upon separation of the donor substrate or sheet and receiver sheet, the imaging layer fractures along the lines defined by the pattern of light and shadow to which the imaging layer has been exposed. Part of the imaging layer is transferred to one of the sheets while the remainder is retained on the other sheet so that a positive image, that is, a duplicate of the original is produced on one sheet while a negative image is produced on the other.

Due to the manipulative steps of exposing the imaging layer to electromagnetic radiation forming a manifold sandwich, providing an electrical field and then separating the manifold sandwich there is a need for a convenient method of producing an electric field across the imaging layer. The use of electrodes on either side of the sandwich has been employed but for obvious reasons, their use does not permit convenient manipulation of the manifold sandwich during the imaging process.

Thus, there is a need for a new process which provides an electric field across the imaging layer during the manifold imaging process steps in a convenient and efficient manner.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a manifold imaging process which will overcome the abovenoted disadvantages.

Another object of this invention is to provide a manifold imaging process wherein the electric field across the imaging layer is provided in a convenient and efficient manner.

Another object of this invention is to provide alternative means of providing an electric field across the imaging layer in the manifold imaging process.

Now, therefore, in accordance with the present invention there is provided a structure comprising a cohesively weak electrically photosensitive imaging layer sandwiched between a donor sheet and a receiver sheet at least one of the sheets being electrically insulating. The electrically insulative sheet is electrically charged so as to carry with it a static electric charge into the manifold sandwich. The static charge in either or both of the sheets of the manifold sandwich provides the electric field required to fracture the imaging layer upon sandwich separation thereby forming a negative and a positive image as described above.

The process of this invention may take many forms. For example, the sandwich of donor sheet, imaging layer and receiver sheet can be drawn between the two wire electrodes which are connected to a source of potential difference. A charge is thereby placed on both surfaces of the electrically insulating material in the sandwich. Alternatively, either or both the receiver sheet and donor sheet can be charged before being brought together in a manifold sandwich. After charging, the imaging layer is then exposed to a pattern of light and shadow representative of the image to be reproduced. Upon separation of the donor and receiver sheets, the imaging layer fractures along the lines defined by the pattern of light and shadow providing a negative image on one of the sheets and a positive image on the opposite sheet. Alternatively, one or both surfaces of the manifold sandwich may be charged by means known in the art, for example, there may be employed corona discharge devices such as those described in U.S. Pat. No. 2,588,699 to Carlson, U.S. Pat. No. 2,777,957 to Walkup, U.S. Pat. No. 2,885,556 to Gundlach, or by using conductive rollers as described in U.S. Pat. No. 2,980,834 to Tregay et al., or by frictional means as described in U.S. Pat. No. 2,297,691 to Carlson or other suitable apparatus.

As stated above, either or both of the donor and receiver sheets may be charged prior to sandwich formation. ln addition, the imaging layer may be exposed to electromagnetic radiation to which it is sensitive either before or after sandwich formation, but if the imaging step is performed after sandwich formation, then at least one of the donor and receiver sheets must be transparent to the electromagnetic radiation employed. The static charge is placed in the donor or receiver sheet by positioning the sheet in electrical communication with a charge bearing member or electrode. The charge bearing member is usually under a potential of from 5,000 to 20,000 volts although other voltages may be employed. The charge transmitted to the insulating layer is in the range of from about 4,000 to about 15,000 volts. 1n the manifold imaging process, by way of example, if a 3 mil thick receiver sheet and a 2 mil thick donor sheet are employed potentials as high as 20,000 volts may be transmitted to the insulating layer or layers. The preferred field strength across the imaging layer is, however, in the range of from 3,000 volts per mil to about 7,000 volts per mil, although a fields of from 1,000 volts per mil up to the electrical breakdown field have been employed.

The electrodes may consist of any suitable-conductive material. Typical conductive electrode materials include aluminum, brass, stainless steel, copper, nickel, zinc and mixtures thereof. Aluminum is preferred because it is readily available and because it is a good conductor. In those instances wherein one of the donor and receiver sheets is conductive it may also serve as an electrode.

The donor substrate and the receiving sheet may consist of any suitable insulating material. Typical insulating materials include polyethylene, polyethylene terephthalate, cellulose acetate, paper, plastic coated paper, such as polyethylene coated paper, and mixtures thereof. Mylar, a polyester formed by the condensation reaction between ethylene glycol and terephthalic acid available from the E. I. DuPont de Nemours and Co., Inc. is preferred because of its physical strength and because it has good insulation qualities.

The imaging layer may comprise any suitable electrically photosensitive material in a binder. Typical electrically photosensitive materials include materials such as: substituted and unsubstituted phthalocyanine; zinc oxide; mercuric sulfide; Algol Yellow (C. I. No. 67,300); cadmium sulfide; cadmium selenide; lndofast brilliant scarlet (C. I. no. 71,140); zinc sulfide; selenium; antimony sulfide; mercuric oxide; indium trisulfide; titanium dioxide; arsenic sulfide; Pb,0,; gallium triselenide; zinc cadmium sulfide; lead iodide; lead selenide; lead sulfide; lead telluride; lead chromate; gallium telluride; mercuric selenide; and the iodides; sulfides; selenides; and tellurides of bismuth, aluminum and mylybdenum. Organic photoconductors, including those complexed with small amounts (up to about percent) of suitable Lewis acids, such as: 4,S-diphenylimidazolidinone; 4,5-diphenylimidazolidinethinone; 4,5 -bis-( 4 '-amino-phenyl)- imidazolidinone; 1,5-cyanonaphthalene; l,4- dicyanonaphthalene; aminophthalodinitrile; nitrophthalidinitrile; l ,2,5,6-tetraazacyclooctatetraene- (2,4,6,8); 3;4-di-(4'methoxy-phenyl)- 7,8-diphenyl-l,2,5,6- tetraazacyclooctatetraene-(2,4,6,8); 3,4-di-(4'phenoxy-phenyl-7,8-diphenyl-l ,2,5 ,6-tetraaza-cyclooctatetraene-( 2,4,6,8 3 ,4,7,8-tetramethoxy-l ,2,5 ,6-tetraazacyclooctatetraene- (2,4,6,8); Z-mercaptobenzthiazole; 2-phenyl-4-diphenylidene-oxazolone; 2-phenyl-4-p-methoxy benzylidene-oxazolone; 6-hydroxy-2phenyl-3-(p-dimethylamino phcnyl)- benzofurane; 6-hydroxy-2,3-di-(p-methoxyphenyl)-benzofurane; 2,3,5,6-tetra-(p-methoxyphenyl)-benzofurane; 2,3,5,6- tetra-(p-methoxy-phenyl)-furo-(3,2f)-benzofurane; 4- dimethylamino-benzylidenebenzhydrazide; 4- dimethylaminobenzylideneisonicotinic acid hydrazide; furfurylidene-(2)-4'-dimethylamino-benzhydrazide; S-benzilidene-amino acenaphthene; 3-benzylidene-amino-carbazole; (4-N, N-dimethyl amino-benzylidene)-p-N, N- dimethylaminoaniline; (2-nitrobenzylidene)-p-bromo-aniline; N, N-dimethyl-N-(2-nitro-4-cyano benzylidene)-p-phenylene-diamine; 2,4-diphenylquinazoline; 2-(4-amino-phenyl)-4-phenyl-quinazoline; 2-phenyl-4-(4'-di-methyl-aminophenyl)-7-methoxy-quinazoline; l,3-diphenyltetrahydroimidazole; l,3-di-(4chlorophenyl)- tetrahydroimidazole; 1,3-di-phenyl-2-4-dimethylamino phenyl)-tetrahydroimidazole; l,3-di-(p-tolyl)-2-[quinolyl-(2'-]- tetrahydroimidazole; 3-(4'-dimethyl amino-phenyl)-5-(4'- methoxyphenyl-G-phenyl-l, 2,4-triazine; 3-pyridil-(4)-5-(4"- dimethyl-amino-phenyl)-6-phenyll ,2,4-triazine; 3,(4-aminophenyl)-5,6-di-phenyl-l,2,4-triazine; 2,5-bis [4-amino-phenyl-( l ')]-l,3,4-triazole; 2,5-bis [4-(N-ethyl-N-acetyl-amino)- amino )-phenyl-( 1)]-l,3,4-triazole; l,5-diphenyl-3-methylpyrazoline; l,3,4,5-tetraphcnyl-pyrazoline; l-methyl-2-(3'4'- di-hydroxymethylene-phenyl)-benzimidazole; 2-(4'-dimethylamino phenyl)-benzoxazole; 2-(4'-methoxyphenyl)- benzthiazole; 2,5-bis-[p-aminophenyl-( l )]-l ,3,4-oxidiazole; 4,S-diphenyl-imidazolone; 3,-aminocarbazole; copolymers and mixtures thereof. Any suitable Lewis acid (electron acceptor) may be employed under complexing conditions with many of the aforementioned more soluble organic materials and also with many of the more insoluble organics to impart very important increases in photosensitivity to those materials. Typical Lewis acids are 2,4,7-trinitro-9fluorenone; 2,4,5,7- tetranitro-9-fluorenone; picric acid; 1,3,5-trinitro-benzene chloranil; benzo-quinone; 2,5-dichlorobenzoquinone; 2-6- dichlorobenzo quinone; chloranil; naphthoquinone-( 1,4); 2,3-di-chloronaphthoquinone-( l ,4); anthraquinone; 2- methyl-anthraquinone; l,4-dimethyl-anthra-quinone; lchloroanthraquinone; anthraquinone-Z-carboxylic acid; 1,5- dichloroanthraquinone, l-chloro-4-nitro-anthraquinone; phenanthrenequinone; acenaphthenequinone; pyranthrenequinone; chrysenequinone; thio-naphthenequinone; anthraquinone-l, 8-disulfonic acid and anthraquinone-2- aldehyde; triphthaloyl-benzene-aldehydes such as bromal, 4- nitrobenzaldehyde; 2,6-di-chloro-benzaldehyde-2, ethoxy-lnaphthaldehyde; anthracene-9-aldehyde; pyrene-3-aldehyde; oxindole-3-aldehyde; pyridine-2,6-dialdehyde, biphenyl-4-aldehyde; organic phosphonic acids such as 4-chloro-3- nitrobenzene-phosphonic acid; nitrophenols; such as 4- nitrophenol and picric acid; acid anhydrides; for example, acetic anhydride, succinic anhydride, maleic anhydride;

phthalic anhydride, tetrachlorophthalic' anhydride; perylene 3,4,9,l0-tetracarboxylic acid and chrysens-2,3,8,9-tetra-carboxylic anhydride; di-bromo maleic acid anhydride; metal-halides of the metals and metalloids of the groups "3, ll through the group VIII of the periodical system, for example: aluminum chloride, zinc chloride, ferric chloride, tin tetrachloride, (stannic chloride); arsenic trichloride; stannous chloride; antimony pentachloride, magnesium chloride, magnesium bromide, calcium bromide, calcium iodide, strontium bromide, chromic bromide, maganous chloride, cobaltous chloride, cobaltic chloride, cupric bromide, ceric chloride, thorium chloride; arsenic triiodide; boron halide compounds, for example: boron trifluoride and boron trichloride; and ketones, such as acetophenone benzophenone; 2-acetylnaphthalene; benzil; benzoin; S-benzoylacenaphthene, biacene-dione, 9-acety-lanthracene, 9-benzoyl-anthracene; 4- (4-dimethylamino-cinncmoyl)- l-acetyl-benzene; acetoacetic acid anilide; indandione-( l,3),-( l-3-diketohydrindene); acenaphthene quinone-dichloride; anisil, 2,2-pyridil; furil, mineral acids such as the hydrogen halides, sulfuric acid and phosphoric acid; organic carboxylic acids; such as acetic acid and the substitution products thereof; monochloro-acetic acid; dichloro-acetic acid; trichloro-acetic acid; phenylacetic acid; and 6-methyl-coumarinylacetic acid (4); maleic acid, cinnamic acid; benzoic acid; 1-(4-diethyl-amino-benzoyl)- benzene-2-carboxylic acid; phthalic acid; and tetrachlorophthalic acid; alpha-beta-dibromo-beta-formylacrylic acid (mucobromic acid); dibromo-maleic acid; 2- bromo-benzoic acid; gallic acid; 3-nitro-2-hydroxyl-l-benzoic acid; 2-nitro phenoxy acetic acid, 2-nitro-benzoic acid; 3-nitro benzoic acid; 4-nitro-benzoic acid; 3-nitro-4-ethoxy-benzoic acid; 2-chloro-4-nitro-l-benzoic acid, Z-chloro 4-nitro-lbenzoic acid, 3-nitro-4-methoxy benzoic acid, 4-nitro-lmethyl-benzoic acid; 2-chloro-5-nitro-l-benzoic acid; 3- chloro-G-nitro-l-benzoic acid; 4-chloro-3-nitro-l-benzolc acid; 5-chloro-3-nitro-2-hydroxy-benzoic acid; 4-chloro-2- hydroxy-benzoic acid; 2,4dinitro-lbenzoic acid; 2-bromo-S- nitro-benzoic acid; 4-chloro-phenyl-acetic acid; 2-chloro-cinnamic acid; 2-cyano-cinnamic acid; 2,4-dichlorobenzoic acid; 3,5-dinitro-benzoic acid; 3,5-dinitro-salycylic acid; malonic acid; mucic acid; acetosalycylic acid; benzilic acid; butanetetra-carboxylic acid; citric acid; cyano-acetic acid; cyclohexane-dicarboxylic acid; cyclo-hexane-carboxylic acid; 9,10- dichloro-stearic acid; fumaric acid; itaconic acid; levulinic acid; (levulic acid); malic acid; succinic acid; alpha-bromo stearic acid; citraconic acid; dibromo-succinic acid; pyrene- 2,3,7,8-tetra-carboxylic acid; tartaric acid; organic sulfonic acid, such as 4-toluene sulfonic acid; and benzene sulfonic acid; 2,4-dinitro-l-methyl-benzene-o-sulfonic acid; 2,6- dinitro-l-hydroxy-benzene-4-sulfonic acid and mixtures thereof.

In addition other electrically photosensitive materials may be formed by complexing one or more suitable Lewis acids with polymers which are ordinarily not thought of as photoconductors. Typical polymers which may be complexed in this manner include the following illustrative materials: polyethylene terephthalate, polyamides, polyimides, polycarbonates, polyacrylates, polymethyl-methacrylates, polyvinyl fluorides, polyvinyl chlorides, polyvinyl acetates, polystyrene, styrenebutadiene copolymers, polymethacrylates, silicone resins chlorinated rubber, and mixtures and copolymers thereof where applicable; thermosetting resins such as epoxy resins, phenoxy resins, phenolics, epoxy-phenolic copolymers, epoxy urea formaldehyde copolymers, epoxy melamine-formaldehyde copolymers and mixtures thereof, where applicable. Other typical resins are epoxy esters, vinyl epoxy resins, tall-oil modified epoxies, and mixtures thereof where applicable. Phthalocyanines are preferred because of their high sensitivity and excellent color,

Any suitable phthalocyanine may be used to prepare the electrically photosensitive layer of the present invention. The phthalocyanine used may be in any suitable crystal form. It may be substituted or unsubstituted both in the ring and straight chain portions. Reference is made to a book entitled Phthalocyanine Compounds by P. iii. Moser and A. L. Thomas, published by the Reinhold Publishing Company, 1963 edition for a detailed description of phthalocyanines and their synthesis. Any suitable phthalocyanine may be used in the present invention. Phthalocyanines encompassed within this invention may be described as compositions having four isoindole groups linked by four nitrogen atoms in such a manner so as to form a conjugated chain, said compositions have the general formula (C H,N ),R,, wherein R is selected from the group consisting of hydrogen, deuterium, lithium, sodium, potassium, copper, silver, beryllium, magnesium, calcium, zinc, cadmium barium, mercury, aluminum, gallium, indium, lanthanum, neodymium, Samarium, europium, gadolinium, dypsprosium, holmium, erbium, thuliurn, ytterbium, luteciurn, titanium, tin, hafnium, lead, silicon, gervanium, thoriurn, vanadium, antimony, chromium, molybdenum, uranium, manganese, iron, cobalt, nickel, rhodium, palladium, osmium, and platinum; and n is a value of greater than and equal to or less than 2. Any other suitable phthalocyanines such as ring or aliphatically substituted metallic and/or nonmetallic phthalocyanines may also be used if suitable. As above noted, any suitable phthalocyanine may be used to prepare the electrically photosensitive layer of the present invention. Typical phthalocyanines are: aluminum phthalocyanine, aluminum polychlorophthalocyanine, antimony phthalocyanine, barium phthalocyanine, beryllium phthalocyanine, cadmium hexadechloro-phthalocyanine, cadmium phthalocyanine, calcium phthalocyanine, cerium phthalocyanine, chromium phthalocyanine, cobalt phthalocyanine, cobalt chlorophthalocyanine, copper 4-arninophthalocyanine, copper bromochlorophthalocyanine, copper 4chlorophthalocyanine, copper 4- nitrophthalocyanine, copper phthalocyanine, copper phthalocyanine sult'onate, copper polychlorophthalocyanine, deuterio-phthalocyanine, dysprosium phthalocyanine, erbium phthalocyanine, europium phthalocyanine, gadolinium phthalocyanine, gallium phthalocyanine, germanium phthalocyanine, hafnium phthalocyanine, halogen substituted phthalocyanine, holrnium phthalocyanine, indium phthalocyanine, iron phthalocyanine, iron polyhalophthalocyanine, lanthanum phthalocyanine, lead phthalocyanine, lead polychlorophthalocyanine, cobalt hexaphenylphthalocyanine, copper pentaphenylphthalocyanine, lithium phthalocyanine, lutecium phthalocyanine, magnesium phthalocyanine, manganese phthalocyanine, mercury phthalocyanine, molybdenum phthalocyanine, naphthalocyanine, neodymium phthalocyanine, nickel phthalocyanine, nickel polyhalophthalocyanine, osmium phthalocyanine, palladium phthalocyanine, palladium chlorophthalocyanine, alkixyphthalocyanine, alkylaminophthalocyanine, alkylmercaptophthalocyanine, aralkylaminophthalocyanine, aryloxyphthalocyanine, arylmercaptophthalocyanine, copper phthalocyanine piperidine, cycloalkylaminophthalocyanine, dialkylaminophthalocyanine, diaralkylaminophthalocyanine, dicycloalkylarninophthalocyanine, hexadecahydrophthalocyanine, imidomethylphthalocyanine, 1,2naphthalocyanine, 2,3naphthalocyanine, octaazaphthalocyanine, sulfur phthalocyanine, tetraazaphthalocyanine, tetra-4-acetylaminophthalocyanine, tetra-4aminobenzoylphthalocyanine, tetra-4- aminophthalocyanine, tetrachlorornethylphthalocyanine, tetradiazophthalocyanine, tetra-4,4-dimethyloctaazaphthalocyanine, tetra-4,S-diphenylenedioxide phthalocyanine, tetra- 4,5-diphenyloctaazaphthalocyanine, tetra(6-methylbenzothiazoyl) phthalocyanine, tetra-p-methylphenylaminophthalocyanine, tetramethylphthalocyanine, tetranapthotriazolylphthalocyanine, tetral-naphthylphthalocyanine, tetea-4-nitrophthalocyanine, tetra-peri-naphthylene- 4, -acta-azaphthalocyanine, tetra-2, 3-phenyleneoxide phthalocyanine, tetrar-phenyl-octaazaphthalocyanine, tetraphenylphthalocyanine, tetraphenyl phthalocyanine tetracarboxylic acid, tetraphenylphthalocyanine tetrabarium carboxylate, tetraphenylphthalocyanine tetra-calcium carboxylate, tetrapyridyphthalocyanine, tetra-d-trifluoromethyl mercaptophthalocyanine, tetra-4-trifluoromethylphthalocyanine, 4, 5-thionaphthene-octaazaphthalocyanine, platinum phthalocyanine, potassium phthalocyanine, rhodium phthalocyanine, samarium phthalocyanine, silver phithalocyanine, silicone phthalocyanine, sodium phthalocyanine, sulfonated phthalocyanine, thorium phthalocyanine, thulium phthalocyanine, tin chlorophthalocyanine, tin phthalocyanine, titanium phthalocyanine, uranium phthalocyanine, vanadium phthalocyanine, ytterbium phthalocyanine, zinc chlorophthalocyanine, zinc phthalocyanine, others described in the Moser text and mix tures, dimers, trimers, oligomers, polymers, copolymers or mixtures thereof.

It is also to be understood in connection with the heterogeneous system, that the electrically photosensitive particles themselves may consist of any suitable one of more of the aforementioned photoconductors, either organic or inorganic, dispersed in, in solid solution in, or copolymerized with, any suitable insulating resin whether or not the resin itself is photoconductive. This particular type of particle may be particularly desirable to facilitate dispersion of the particle, to prevent undesirable reactions between the binder and the photosensitive material or between the photosensitive material and the activator and for similar purposes. Typical resins include polyethylene, polypropylene, polyamides, polymethacrylates, polyacrylates, polyvinyl chlorides, polyvinyl acetates, polystyrene, polysiloxanes, chlorinated rubbers, polyacrylonitrile, epoxies, phenolics, hydrocarbon resins and other natural resins such as rosin derivatives as well as mixtures and copolymers thereof. Polyethylene is preferred because of its low-melting point and because it is readily available.

The binder materials in the heterogeneous imaging layer or the material used in conjunction with the pigment materials in the homogeneous layer, where applicable, may comprise any suitable cohesively weak insulating material or materials which can be rendered cohesively weak. Typical materials include: microcrystalline waxes such as: Sunoco 1290, Sunoco 5825, Sunoco 985, all available from Sun Oil Co.; Paraflint RG, available from the Moore and Munger Company; paraffin waxes such as: Sunoco 5512, Sunoco 3425, available from Sun Oil Co.; Sohio Parowax, available from Standard Oil of Ohio; waxes made from hydrogenated oils such as: Capitol City 1380 wax, available from Capitol City Products, Columbus, Ohio; Caster Wax L-2790, available from Baker Caster Oil Co.; Vitikote L-304, available from Duro Commodities; polyethylenes such as: Eastman Epolene N-l l, Eastman Epolene C-l2, available from Eastman Chemical Products; Polyethylene DYJT, Polyethylene DYLT, Polyethylene DYNF, Polyethylene DYDT, all available from Union carbide; Marlex TR 822, Marlex 1478, available from Phillips Petroleum Co.; Epolene C-l3, Epolene C-lO, available from Eastman Chemical Products; Polyethylene AC8, Polyethylene AC612, Polyethylene AC324, available from Allied Chemicals; modified styrenes such as: Piccotex 75, Piccotex 100, Piccotex 120, available from Pennsylvania lndustrial Chemical; Vinylacetate-ethylene copolymers such as: Elvax Resin 210, Elvax Resin 310, Elvax Resin 420, available from Du- Pont; Vistanex Mll, Vistanex L-80, available from lEnjay Chemical Co.; vinyl chloride-vinyl acetate copolymers such as: Vinylite VYLP, available from union Carbide; styrenevinyl toluene copolymers; polypropylenes; an mixtures thereof. The use of an insulating binder is preferred because it allows the use of a larger range of electrically photosensitive pigments.

A mixture of microcrystalline wax and polyethylene is preferred because it is cohesively weak and an insulator.

Where the imaging layer does not have sufficiently lowcohesive strength at the time of imaging, it must be activated as described above. Typical activating fluids, as further described below, may include any material which will reduce the cohesive strength of the imaging layer. The activating fluid is ordinarily applied to the imaging layer immediately before the imaging operation takes place. Any suitable volatile or nonvolatile activating fluid may be employed. Typical materials include kerosene, carbon tetrachloride, petroleum ether, silicone oils, such as dimethyl polysiloxanes, long chain aliphatic hydrocarbon oils such as those ordinarily used as transformer oils, benzene, toluene, xylene, hexane, acetone, vegetable oils, or mixtures thereof. Kerosene is preferred because it is readily available and evaporates quickly.

The advantages of this improved method of imaging will become apparent upon consideration of the detailed disclosure of the invention especially when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side sectional view of a manifold sandwich for use in the invention.

FIG. 2 is a side sectional view diagrammatically illustrating the process steps of this invention.

Referring now to FIG. 1, imaging layer 2 comprising photosensitive particles 4 dispersed in binder 3 is deposited on an insulating donor sheet 5. The image receiving portion of the manifold set comprises an insulating receiver sheet 6. Sheets 5 and 6 are preferably insulating materials so that they will hold a charge placed on their surface.

Referring now to FIG. 2, the first step in the imaging process is the activation step. Although the activator may be applied by any suitable technique such as with a brush, with a smooth or rough surfaced roller, by flow coating, by vapor condensation or the like, FIG. 2 which diagrammatically illustrates the process steps of this invention shows the activator fluid 23 being sprayed onto image layer 12 of the manifold set from a container 24. Following the deposition of this activator fluid the set is closed by a roller 26 which also serves to squeeze out any excess activator fluid which may have been deposited. The activator lowers the cohesive strength of imaging layer 12. In certain instances the first two steps of the imaging process as diagrammatically illustrated in FIG. 2 may be omitted, thus for example, a manifold set may be supplied wherein imaging layer 12 is initially fabricated to have a low enough cohesive strength so that activation may be omitted and receiving layer 16 may be placed on the surface of imaging layer 12 at the time when that layer is coated on substrate 17 either from solution or from a hot melt. It is generally preferable, however, to include an activation step in the process because stronger and more permanent imaging layers may then be provided which can withstand storage and transportation prior to imaging.

Once the proper physical properties have been imparted to imaging layer 12 and the receiving sheet 16 has been placed on layer 12, an electrical field is applied across the manifold set through electrodes 18 and 21 which are connected to potential source 28 and resistor 30. Although FIG. 2 shows the manifold sandwich not coming in contact with either electrode 18 or 21 since the receiver sheet and the donor sheet are preferably insulating materials, they may contact one or both electrodes during the charging operation. Preferably, the sandwich will contact one electrode to serve as a guide and be spaced 1 to 3 mils from the other electrode to prevent binding.

Alternatively, the charging electrode may be a corona discharge, a roller, roller 26 could be conductive, for example, and be used to charge in place of electrode 18, a sharp edge or a friction charging device such as a fur covered roller.

The sign of the charge as shown on electrodes 18 and 21 may also be reversed, electrode 18 being made the negative electrode and electrode 21 being made the positive electrode. The charge bearing manifold set then moves on to imaging station 27 where it is exposed to light image 29. Light image 29 may be light projected through a transparency or light information projected from an opaque subject. In a continuous operation the light image preferably is projected through a slit in such manner that there is little or no relative movement between the projected light image and the manifold set. The manifold sandwich then passes roller 32 which acts as a guide for the manifold sandwich and as a bearing point for the stripping apart of the receiver and donor sheets. Alternatively, roller 32 may be a sharp edge, a rod, or a wire. Upon separation of substrate 17 and receiving sheet 16 imaging layer 12 fractures along the edges of exposed areas and at the surface where it had adhered to substrate 17. Accordingly, once separation is complete, exposed portions of imaging layer 12 are retained on one of sheets 17 and 16 while unexposed portions are retained on the other sheet which provide a positive image on one sheet and a negative image on the other sheet.

The following examples further specifically illustrate the present invention. The examples below are intended to illustrate various preferred embodiments of the improved imaging method. The parts and percentages are by weight unless otherwise indicated.

EXAMPLE I A commercial metal-free phthalocyanine is first purified by 9-dichlorobenzene extraction to remove organic impurities. Since this extraction step yields the less sensitive beta crystalline form, the desired x" form is obtained by dissolving about grams of beta in approximately 600 cc. of sulfuric acid, precipitating it by pouring the solution into about 3,000 cc. of ice water and washing with water to neutrality. The thus purified alpha phthalocyanine is then salt milled for 6 days and desalted by slurrying in distilled water, vacuum filtering water washing, and finally methanol washing until the initial filtrate is clear. After vacuum drying to remove residual methanol the X" form phthalocyanine thus produced is used to prepare the imaging layer according to the following procedure: About 5 grams of the x" form phthalocyanine is added to about 5 grams of Algol Yellow GC, l,2,5,6-di-(C,C-diphenyl) thiazole-anthraquinone, C.l. No. 67300, available from General Dyestuffs, and about 2.8 grams of purified Watchung Red B, 1-(4-rnethyl-5-chloroazobenzene-2' -sulfonic acid)- 2-hydroxy-3-naphthoic acid, C.l. No. l5865, available from E. I. DuPont de Nemours & Co. which is purified as follows: Approximately 240 grams of the Watchung Red B is slurried in about 2,400 milliliters of Sohio Odorless Solvent 3440, a mixture of kerosene fractions available from the Standard Oil Company of Ohio. The slurry is then heated to a temperature of about 65 C. and held there for about one-half hour. The slurry is then filtered through a glass sintered filter. The solids are then reslurried with petroleum ether (90 to C.) available from Matheson, Coleman and Bell Division of the Matheson Company, East Rutherford, New Jersey and filtered through a glass sintered filter. The solids are then dried in an oven at about 500 C.

About 8 grams of Sunoco Microcrystalline Wax Grade 5825 having an ASTM-D-l27 melting point of 151 F. and about 2 grams Paraflint R. G., a low molecular weight paraffinic material, available from the Moore & Munger Company, New York City, and about 320 milliliters of petroleum ether (90 to 120 C.) and about 40 milliliters of Sohio Odorless Solvent 3440 are placed with the pigments in a glass jar containing liinch flint pebbles. The mixture is then milled by revolving the glass jar at about 70 r.p.m. for about 16 hours. The mixture is then heated for approximately 2 hours at about 45 C. and allowed to cool to room temperature. The mixture is then ready for coating on the donor substrate. The pastelike mixture is then coated in subdued green light on 2 mil Mylar (a polyester formed by the condensation reaction between ethylene glycol and terephthalic acid available from E. l. DuPont de Nemours & Co., Inc.) with a No. 36 wire wound drawdown rod to produce a coating thickness when dried of approximately 7% microns. The coating and 2 mil Mylar sheet is then dried in the dark at a temperature of about 33 C. for one-half hour. A receiver sheet also of 2 mil Mylar is placed over the donor. The receiver sheet is then lifted up and the imaging layer activated with one quick brush stroke of a wide camel's hair brush saturated with Sohio 3440. The receiver sheet is then lowered back down and a roller is rolled slowly once over the closed manifold set with light pressure to remove excess solvent. Two electrodes consisting of A-inch diameter copper rods 3 inches long are placed in spaced relationship one above the other at a distance of about 7 mils. The upper electrode is connected to the positive terminal of a 9,000 volt DC power supply and grounded. The lower electrode is then connected to the negative terminal of the power supply. The manifold sandwich is drawn with the receiver side up through the space between the two electrodes while a potential is applied between the electrodes. To prevent arching the manifold sandwich width provided is about one-half inch wider than the electrodes are long. For example, if approximately 3-inch electrodes are used, a manifold sandwich of about 3% inches width is used. The lit-inch overlap on each end of the electrodes prevents sparking between the two electrodes. The charged manifold sandwich is then placed on a glass plate. A white incandescent light image is then projected through the glass plate using a 300-watt Bell & Howell Headliner Model 70820 Slide Projector having a piece of Trans-Positive Sheet (Frosted) available from Xerox and a variable aperture placed in front of it. The distance from the projector to the imaging donor layer is approximately 60 inches. The light incident on the imaging layer is adjusted to approximately 1 foot-candle. The imagewise exposure continues for 0.3 seconds resulting in a total exposure of 0.3 foot-candle-seconds. After exposure the receiver sheet is peeled from the set yielding a pair of excellent quality images with a positive image adhering to the donor sheet and a negative image adhering to the receiver sheet.

EXAMPLE ll The experiment of example I is a repeated except that the upper electrode is replaced by a l-inch aluminum roller and the lower electrode is replaced by a flat piece of copper 3 inches long, one-fourth inch wide and about 5 mils thick spaced 7 mils apart. The roller and copper strip are connected to the power source of example I. Upon separation of the set after imaging a high-quality positive image adheres to the donor sheet and a high-quality negative image adheres to the receiver sheet.

EXAMPLE ill The experiment of example I is repeated except that the upper electrode is connected to the negative terminal of the power supply and the positive terminal is connected to the lower electrode and grounded. Upon separation of the receiver and donor sheets subsequent to imaging a high-quality negative image is found on the receiver sheet and a positive image on the donor sheet.

EXAMPLE lV About 2% grams of x form phthalocyanine prepared as in example I, about 2% grams of Benzidene Yellow YT-4ll available from the Holland Suco Color Co., Holland, Michigan, and approximately 60 cc. of the petroleum ether of example I are placed in a glass jar with /-inch flint pebbles and milled as in example l for about 16 hours.

Next about 1 mol of alpha methyl styrene and about 1 mol of vinyl toluene are added to sufficient xylene to produce a 40 percent solution. A catalytic amount of boron trifluoride etherate is then added and the mixture stirred until polymerization is complete. After polymerization, sufficient methanol is added to decompose any boron trifiuoride present, the polymer is then isolated by steam distillation. The resulting polymer is available as Piccotex 100 from the Pennsylvania Industrial Chemical Company.

About 2% grams of the Piccotex 100 is added to about 3 grams of polyethylene DYLT available from the Union Carbide Company, and about 1% grams of Paraflint RG and about one-half gram of Elvax 420, an ethylene-vinyl-acetate copolyrner available from the E. l. DuPont de Nemours Company. The mixture is then dissolved in about 180 milliliters of Sohio 3440 at about the boiling point. The solution is then allowed to cool to room temperature. The solution is then added to the mixture ofpigments and milled as in example I for about 16 hours. The milled mixture is then heated to a temperature of approximately 65 C. and then allowed to cool to approximately room temperature. The resulting paste is then ready for coating on the donor substrate. The paste is then coated in subdued green light on Z-mil Mylar with a No. 36 wire wound drawdown rod to produce a coating thickness dry of about 7 /2 microns. The coated donor is then heated in the dark to about 33 C. for about one-half hour in order to dry it. A receiver sheet also of 2-mil Mylar is placed over the imaging layer. The receiver sheet is then lifted up and the imaging layer activated with one quick brush stroke of a wide camel's hair brush saturated with Sohio Solvent 3440. The: receiver sheet is then lowered back down and a roller is rolled slowly once over the closed manifold set with light pressure to remove any excess Sohio. The manifold sandwich is then charged and imaged as in example I with the exception that. imagewise exposure is continued for 0.4 seconds. Upon separation of the sheets a negative image is observed adhering to the receiver sheet and a positive image adhering to the donor sheet.

EXAMPLE V The experiment of example 1V is repeated except that the manifold sandwich is charged as in example ll. After imaging the receiving and donor sheets are separated. A high-quality quality negative image is observed adhering to the receiver sheet and a (high-quality positive image is observed adhering to the donor sheet.

EXAMPLE VI A commercial metal-free phthalocyanine is first purified by O-dichlorobenzene extraction to remove organic impurities. Since this extraction step yields the less sensitive beta crystalline form, the desired x form is obtained by dissolving about grams of beta in approximately 600 cc. of sulfuric acid, precipitating it by pouring the solution in about 3,000 cc. of ice water and washing with water to neutrality. The thus purified alpha phthalocyanine is then salt milled for 6 days and desalted by slurrying in distilled water, vacuum filtering, water washing, and finally methanol washing until the final filtrate is clear. After vacuum drying to remove residual methanol the x form phthalocyanine thus produced is used to prepare the imaging layer according to the following procedure: About 5 grams of the 1: form phthalocyanine is added to about 5 grams of Algol Yellow GC, l,2,.5,6-di-(C,C'-diphenyl) thiazole-anthraquinone, C.l. No. 67300, available from General Dyestuffs, and about 2.8 grams of purified Watchung Red B, l-(4-methyl-5"-chloroazobenzene-2'-sulfonic acid)- 2-hydroxy-3-naphthoic acid, C.I. No. 15865, available from E. l. DuPont de Nemours & Co. which is purified as follows: Approximately 240 grams of the Watchung Red B is slurried in about 2,400 milliliters of Sohio Odorless Solvent 3440, a mixture of kerosene fractions available from the Standard Oil Company of Ohio. The slurry is then heated to a temperature of about 65 C. and held there for about one-half hour. The slurry is then filtered through a glass sintered filter. The solids are then reslurried with petroleum ether (90 to C.) and filtered through a glass filter. The solids are then dried in an oven at about 50 C.

About 8 grams of Sunoco Microcystalline Wax Grade 5825 having an ASTM-D-l27 melting point of 151 F. and about 2 grams Paraflint R.G., a low molecular weight parafimic material, available from the Moore and Munger Company, New York City, and about 320 milliliters of petroleum ether (90 to 120 C.) and about 40 milliliters of Sohio Odorless Solvent 3440 are placed with the pigments in a glass jar containing /2-inch flint pebbles. The mixture is then milled by revolving the glass jar at about 70 rpm. for about 16 hours. The mixture is then heated for approximately 2 hours at about 45 C. and allowed to cool to room temperature. The mixture is then ready for coating on the donor substrate. The pastelike mixture is then coated in subdued green light on 2-mil. Mylar (a polyester formed by the condensation reaction between ethylene glycol and terephthalic acid available from E. I. Du- Pont de Nemours 8r. Co., Inc.) with a No. 26 wire wound drawdown rod to produce a coating thickness when dried of approximately 75; microns. The coating is then dried in the dark. The coated Mylar sheet is passed between a pair of conductive aluminum rollers which are connected to a DC power supply of about 10,000 volts. The aluminum rollers contact the surface of the imaging layer and the lower surface of the donor sheet. To prevent arcing, the donor sheet width is about onehalf inch greater than the width of the aluminum rollers. For example, if approximately 3-inch rollers are used, a donor sheet of about 3% inches width is employed. The A-inch overlap on each end of the electrodes prevents sparking between the rollers. The charged donor is then placed on a glass plate with the imaging layer facing away from the plate. The imaging layer is exposed with a white incandescent light using a 300-watt Bell & Howell Headliner Model 70820 slide projector having a variable aperture placed in front of it. The light incident on the imaging layer is adjusted to approximately foot-candles. The imagewise exposure continues for 0.2 seconds resulting in a total exposure of l foot-candle-second. After exposure, the imaging layer is activated by applying a coating of Sohio Odorless solvent 3440, a kerosene fraction obtained from the Standard Oil Company, by means of a wide camel's hair brush saturated with the solvent. A sheet of aluminized paper is then lowered into contact with the imaging layer to act as a receiver and is applied with light pressure to remove excess solvent. The aluminized paper and the side of the charged donor sheet opposite the imaging layer are interconnected by means of an electrically conductive material. While connected, the receiver sheet is then peeled from the imaging layer whereupon the imaging layer fractures yielding a pair of excellent quality images with a positive image adhering to the receiver sheet and a negative image adhering to the donor sheet.

EXAMPLE VII The procedure of example I is repeated except that the receiver sheet employed is a clear sheet of 2 mil thick Mylar and the aluminized paper is laid over the Mylar. Upon separation of the receiver sheet from the imaging layer a pair of improved quality images are obtained with a positive image adhering to the receiver sheet and a donor image adhering to the Mylar receiver sheet.

EXAMPLE VIII An imaging layer comprising electrically photosensitive materials dispersed in a binder is first prepared. About 100 parts of Naphthol Red B, Code 7575, available from American Cyanamide Company, is dissolved in reagent grade ethy1ene-diamine. The solution is filtered immediately through course filter paper and the filtrate mixed with an equal volume of reagent grade is removed by means of a centrifuge. After separating the ethylenediamine and alcohol, the electrically photosensitive material is washed and filtered with successive amounts of isopropanol, a 2:1 volume mixture of isopropanol and de-ionized water and five washings with deionized water until the filtrate is neutral. Finally, the material is washed with dimethyl-formamide and methanol in succession until the filtrates have a pale yellow color. The Naphthol Red B is then dried at 40 C. under vacuum. About 2.5 parts of the purified Naphthol Red B is combined with about 0.5 parts of Benz Yellow, code -0535 available from the Hilton Davis Chemical Company. The Benz Yellow is purified by solvent extraction in an organic solvent. The Naphthol Red B and Benz Yellow are combined with about 45 part of naphtha and ball milled for 4 hours.

A binder material is prepared by combining about 1.5 parts of Paraflint RG, a low molecular weight parafinic material available from the Moore and Munger Co., New York City; about three parts of Polyethylene DYLT available from Union Carbide Corporation; about 0.5 parts of a vinyl acetateethylene copolymer available as Elvax 420 from E. I. DuPont de Nemours Inc. and about 2.5 parts of a modified polystyrene available as Piccotex from Pennsylvania Industrial Chemical Co. with about 15 parts of Sohio Odorless Solvent 3440. The mixture is heated until dissolved and then cooled. About 45 parts of isopropyl alcohol is added and the mixture is milled in the ball mill for 15 minutes together with the Naphthol Red B and Benz Yellow. The resulting imaging material is then coated on 3-mil Mylar with a doctor knife set at a gap of 4.4 mil to produce a donor. The donor is dried at a temperature of about 90 F. After drying, the imaging layer is exposed to a pattern of light from an incandescent white light source of 45 ft.-candles for a period of 3 minutes. Immediately after exposure the donor is passed between a pair of conductive rollers connected to a power source so as to provide a DC potential of about 10,000 volts between the rollers. The imaging layer is thus charged to a negative polarity. The imaging layer is then contacted with a film of polypropylene wet with activator. After pressing the polypropylene film against the imaging layer with light pressure, the polypropylene receiver is connected to the positively charged side of the donor sheet by means of an electrically conductive material and then stripped from the imaging layer. The imaging layer fractures yielding a pair of excellent quality images with a positive image adhering to the polypropylene sheet and a negative image adhering to the donor sheet.

EXAMPLE IX About 2% grams ofx form of phthalocyanine prepared as in example I, about 2% grams of Benzidene Yellow and about 2.8 grams of Irgazine Red available from the Geigy Chemical Co. are added to about milliliters of petroleum ether. at 90l20 C. and milled as in example I for about 16 hours. The mixture is then added to a wax binder prepared as described in example I and milled as in example I for about 16 hours. The mixture is heated to a temperature of approximately 65 C. for approximately 2 hours. The mixture is then allowed to cool to approximately room temperature at which time the paste is then coated in subdued green light on a l-mil Mylar sheet with a No. 26 wire wound drawdown rod to produce a coating thickness after drying of about 7 /2 microns. The donor is then dried in the dark at a temperature of about 33 C. for about 30 minutes.

A sheet of polystyrene having a thickness of 2 mils is electrically charged by passing the sheet between a pair of spaced rollers which are connected to a power source which provides a potential of about 10,000 volts DC between the rollers. The charged polystyrene is then brought in contact with the imaging layer on the donor sheet prepared as described above which is now activated by a coating of Sohio Solvent 3440. The side of the polystyrene charged positive is facing the imaging layer. The thus formed sandwich is then passed between a pair of uncharged aluminum rollers which are connected to a common ground. The imaging layer is then exposed through the donor sheet to a pattern of incandescent white light to provide a total light incident of about 5 foot-candle-seconds. After exposure, the sandwich is separated whereupon the imaging layer fractures in imagewise configuration with a positive image adhering to the donor sheet and a negative image adhering to the polystyrene receiver sheet.

EXAMPLE X Example IX is repeated with the exception that the charged polystyrene is inverted so that the side charged negative is facing the imaging layer. After exposure the sandwich is separated whereupon the imaging layer fractures in imagewise configuration as in example IX.

EXAMPLE XI The procedure of example IX is repeated except that a sheet of bond paper is inserted between the charged polystyrene sheet and the imaging layer prior to passing thesandwich between the rollers. Upon separation of the sandwich the imaging layer fractures in imagewise configuration with a positive image on the donor sheet and a negative image adhering to the bond paper.

EXAMPLE XII The procedure of example V1 is repeated with the exception that the donor is electrically charged by means of a corona discharge device instead of a pair of aluminum rollers. Upon separation of the sandwich the imaging layer fractures yielding a pair of excellent quality images with a positive image adhering to the donor sheet and a negative image adhering to the receiver sheet.

EXAMPLE XIII The procedure of example I is repeated except that the imaging layer is not activated. Upon separation of the sandwich no image is obtained and the imaging layer is not fractured. While the donor is still charged the imaging layer is contacted with an aluminum plate which is wet with Sohio Odorless Solvent 3440. A sheet of aluminized paper is placed over the donor and is connected to the aluminum plate by means of an electrically conductive wire. While connected the donor and the paper are lifted from the aluminum plate whereupon the imaging layer fractures in imagewise configuration leaving a positive image on the aluminum plate and a negative image on the donor sheet.

As indicated in the above examples the electric field across the manifold sandwich can be supplied by a static charge in one or two electrically insulative layers. When only one charged layer or sheet is employed, the field is extended across the manifold sandwich by means of an electrically conducting medium placed on the opposite side of the sandwich an electrically interconnecting such medium with the charged layer. The methods or means by which such interconnection can be made varies greatly. Conductive wires, sheets, rods, or particulate material such as encased graphite can be employed to interconnect the conductive medium with the charged layer. Preferably the manifold sandwich is placed between two conductive layers which are electrically interconnected. In addition, the conductive media, as indicated in the above examples, can also function as a donor or receiver sheet in the imaging process. Other means to extend the electric field across the manifold sandwich will occur to those skilled in the art and the above examples merely illustrate the manner by which the field can be extended.

Although specific components and proportions have been stated in the above description of preferred embodiments of the invention, other typical materials as listed above is suitable may be used with similar results. In addition, other materials may be added to the mixture to synergize, enhance, or otherwise modify the properties of the imaging layer. For example, various dyes, spectral sensitizers, or electrical sensitizers such as Lewis acids may be added to the several layers.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of the invention.

What is claimed is:

1. An imaging process which comprises providing an electrically photosensitive imaging layer structurally fracturable in response to the combined effects of an electric field and exposure to electromagnetic radiation to which said layer is sensitive sandwiched between a donor sheet and a receiver sheet, at least one of said sheets being at least partially transparent to electromagnetic radiation to which said layer is sensitive, subjecting said imaging layer to an electric field which field is supplied by a static charge on one of the donor and receiver sheets, said charged sheet being electrically insulating by electrically-interconnecting said sheets to place said electric field across said sandwich, exposing said imaging layer to imagewise electromagnetic radiation to which said layer is sensitive and separating said sandwich while under sal field whereby said imaging layer fractures in imagewise configuration.

2. The process of claim 1 wherein the electric charge is in the range of from about 1,000 volts per mil to about 7,000 volts per mil of electrically insulating material.

3. The method of claim 1 wherein the electric field is provided by a static charge in the receiver sheet and said field is extended across said sandwich by means of electrically interconnected conductive media provided on said donor and receiver.

4. The method of claim 1 wherein the electric field is provided by a static charge in the donor sheet and said field is extended across said sandwich by means of electrically intercon nected conductive media provided on said donor and receiver.

5. The method of claim 1 wherein said static charge is accomplished by frictional means.

6. The method of claim 1 insulating wherein said imaging layer comprises metal free phthalocyanine in an insulating binder.

7. The method of claim 1 wherein said imaging layer comprises an electrically photosensitive material dispersed in an insulating binder.

8. The method of claim 1 further including the step of applying an activator fluid to said imaging; layer prior to separating the sandwich said fluid rendering said imaging layer structurally fracturable in response to the combined efiects of an electric field and exposure to electromagnetic radiation to which said layer is sensitive.

9. The method of claim 1 wherein the electrically photosensitive material is an organic material.

10. The method of claim 6 wherein said binder is a thermoplastic electrically insulating composition.

11. An imaging process which comprises providing an electrically photosensitive imaging layer coated on a dielectric donor sheet, placing a static electric charge on said sheet, exposing said imaging layer to an imagewise pattern of electromagnetic radiation to which said imaging layer is sensitive, contacting said imaging layer with an activator fluid thereby rendering said layer structurally fracturable in response to the combined effects of an electric field and exposure to electromagnetic radiation to which said layer is sensitive and with a receiver sheet, electrically interconnecting said charged donor sheet with said receiver sheet while contacting said imaging layer and separating said donor sheet from said conductive material whereby said imaging layer fractures in imagewise configuration.

12. The method of claim 11 wherein said dielectric donor sheet is electrically charged by passing said donor sheet between two oppositely charged electrodes in spaced relationship.

13. The method of claim 11 wherein said donor sheet is electrically charged by means of a corona discharge device.

14. The method of claim 11 wherein said receiver sheet is electrically conductive.

15. The method of claim 11 wherein said receiver sheet is electrically insulating.

16. The method of claim 11 wherein said static charge is provided by passing said donor sheet between two oppositely charged electrodes at least one of said electrodes being a conductive roller.

17. The method of claim 11 wherein said static charge is accomplished by frictional means.

18. The method of claim 11 wherein: said static charge is provided by passing said donor sheet through the ionization area of at least one corona discharge device.

10. The method of claim 1 wherein said imaging layer comprises an electrically photosensitive material dispersed in an insulating binder.

20. The method of claim 19 wherein said electrically photosensitive material is an organic material. 

2. The process of claim 1 wherein the electric charge is in the range of from about 1,000 volts per mil to about 7,000 volts per mil of electrically insulating material.
 3. The method of claim 1 wherein the electric field is provided by a static charge in the receiver sheet and said field is extended across said sandwich by means of electrically interconnected conductive media provided on said donor and receiver.
 4. The method of claim 1 wherein the electric field is provided by a static charge in the donor sheet and said field is extended across said sandwich by means of electrically interconnected conductive media provided on said donor and receiver.
 5. The method of claim 1 wherein said static charge is accomplished by frictional means.
 6. The method of claim 1 insulating wherein said imaging layer comprises metal free phthalocyanine in an insulating binder.
 7. The method of claim 1 wherein said imaging layer comprises an electrically photosensitive material dispersed in an insulating binder.
 8. The method of claim 1 further including the step of applying an activator fluid to said imaging layer prior to separating the sandwich said fluid rendering said imaging layer structurally fracturable in response to the combined effects of an electric field and exposure to electromagnetic radiation to which said layer is sensitive.
 9. The method of claim 1 wherein the electrically photosensitive material is an organic material.
 10. The method of claim 6 wherein said binder is a thermoplastic electrically insulating composition.
 11. An imaging process which Comprises providing an electrically photosensitive imaging layer coated on a dielectric donor sheet, placing a static electric charge on said sheet, exposing said imaging layer to an imagewise pattern of electromagnetic radiation to which said imaging layer is sensitive, contacting said imaging layer with an activator fluid thereby rendering said layer structurally fracturable in response to the combined effects of an electric field and exposure to electromagnetic radiation to which said layer is sensitive and with a receiver sheet, electrically interconnecting said charged donor sheet with said receiver sheet while contacting said imaging layer and separating said donor sheet from said conductive material whereby said imaging layer fractures in imagewise configuration.
 12. The method of claim 11 wherein said dielectric donor sheet is electrically charged by passing said donor sheet between two oppositely charged electrodes in spaced relationship.
 13. The method of claim 11 wherein said donor sheet is electrically charged by means of a corona discharge device.
 14. The method of claim 11 wherein said receiver sheet is electrically conductive.
 15. The method of claim 11 wherein said receiver sheet is electrically insulating.
 16. The method of claim 11 wherein said static charge is provided by passing said donor sheet between two oppositely charged electrodes at least one of said electrodes being a conductive roller.
 17. The method of claim 11 wherein said static charge is accomplished by frictional means.
 18. The method of claim 11 wherein said static charge is provided by passing said donor sheet through the ionization area of at least one corona discharge device.
 19. The method of claim 1 wherein said imaging layer comprises an electrically photosensitive material dispersed in an insulating binder.
 20. The method of claim 19 wherein said electrically photosensitive material is an organic material. 